Manufacture of para-chloro-ortho



.35 nitro-anisole.

Patented Oct. 6, 1936 l MANUFACTURE OF PARA-CHLORO-ORTHO- NITRO-ANISOLE Miles Augustinus Dahlen and Elmer Ellsworth Fleck, Wilmington, Del., assignors to E. I. du Pont de Nemours & Company, Wilmington, DeL, a corporation of Delaware No Drawing. Application December 7, 1935,

Serial No. 53,426

3 Claims. (Cl. 260-143) A. This invention relates to a method for preyl alcohol ratio being held constant, the velocity paring 4chloro-2-nitro-anisole, hereinafter desof the reaction is markedly affected by the alignated as para-chloro-ortho-nitro-aniso1e, a kali concentration, and to attain an optimum substance which is known and has been used rate of reaction the. alkali concentration should 5 n in ry. I ha be n pr par y olving be held not too far below; that at which excessive 5 nitro-para-dichloro-benzene in methanol, haatside reactions appear. ing the solution to a boil, and adding caustic G. In carrying out the'reaction, the reaction alkali. vessel is charged with nitro-para-dichloro-ben- B. The procedure, as described by Brand and zene, methyl alcohol, and suflicient caustic al- Pabst, J. Pr. (2) 120 205 (1929), states that the ,kali to give the desired concentration; the reac- 10 r ti n is x i ly exothermic. n is tion mass is agitated and heated to a preferred ce pan ed by V gO OIJS boiling, Producing mac temperature, and. a strong solution of caustic terial contaminated With potassium chloride, and alkali is added t a rate t t produces t most Whlch must be pumfied to remove unchanged favorable concentration at each stage of the nitro-para-dichloro-benzene. l5

process. When the reaction 15 complete, the oii ttttii i t tfiiittg 3221110 33 if? iii: product may be isolaieiby any standard proved process of making ortho-nitro-anisole. dure The 9 t for i P be We have discovered that the said improved procnearly vneutrahzed Wlth dllut? f q the ass may be applied to the making of excess alcohol removed by d stillation, and the 20 ortho-nitro-anisole. When nitro-para-dichloroproduct? Washed Wlth Water to remove the Salt benzene is reacted with methyl alcohol and and a Water Soluble lmpurities which y be caustic the product is 1-methoxy-2-nitro-4-chlo- Contamedy The D d Separates as an y ro-benzene, and so far as we have been able to layer a q y Solid; depending O t g determine is never 4-methoxy or dimethoxy. temperature, and is of exceptional purity.

D. It is an object of our invention to improve H. The material of which the reaction vessel the process of manufacturing para-chloro-orthois made has a distinct'effect on the process, some nitro-anisole from nitro-para-dieh OrWben e e materials. inducing undesirable side reactions. y reaction With methyl alcohol and alkali- Glass or other siliceous materials, such as siliother object of the invention is to eliminate from ate ename11ed metal, have'no appreciable effect 30 the process deleterious side reactions and danon the reaction. Nickel is also, a valuable gers Which attended the opemlPn 01d terial, ranking but little below the siliceous maprocess. Another ob ect of the invention is to terials this respect Copper and alloys Such prepare a superior grade of pam'chloro'ortho' as bronze, Monel metal, and the so-called stainless steels are of a lower order, but exercise only a small adverse effect. Iron and steel both affect E. The objects of this invention are accomlished, enerally speaking, by reacting nitrogarwdicfilormbenzene with methyl alcohol in the reaction deleterlously, apparently by catalyzthe presence: of caustic alkali, the concentramg t lfeductlPn of h F body? when the 40 tion of the caustic alkali atthe start being less reactlon 15 earned P equlpment of t type 40 than that at which deleterious side reactions or under standard conditions, the product is hightemperatures are evolved, and the addition to 3 colored, high in Chlorine Content, and p0 n the reaction mass of caustic alkali during the quality. If useful products are to be obtained, process being at substantially the rate of conmuch milder reaction conditions must be used sumption. in such vessels. 45

F. The r a t n a a be considered a I. In the following examples, which illustrate three component System, Containing -P but do not limit the invention, the alkali condich1rbenZene"methy1 h and f We centration is expressed in terms of normality, have discovered that, at any given reaction temwhich means the concentration of alkali in pera'ture Wlth glven who of mtro'palta-dl' equivalent units per liter of reaction mass at the 50 chlormpeqzene to methyl h theta 15 an reaction temperature. Normality may be evaluupper limit of alkali concentration which must t d b not be exceeded if undesirable side reactions are e y 15 equa to be avoided. However, with the factors of tem- 1000W perature and nitro-para-dichloro-benzene-meth- VM 55 where: N is the normality,

W is the weight of alkali in any volume V of solution at reaction temperature,

and

M is the weight of one equivalent of alkali. For bases such as sodium or potassium hydroxide this is the molecular weight.

All quantities are parts by weight, and the methyl alcohol strengths are given as percent by weight.

Eramm le I 672 parts of 95% methyl alcohol, 17 parts of solid sodium hydroxide (95% purity) and 192 parts of nitro-para-dichloro-benzene are added to a copper reaction vessel fitted with agitation, a reflux condenser and coils for heating or cooling. The temperature is raised to 68 C. An aqueous solution of sodium hydroxide of 45% strength is added as required to maintain the alkali concentration at 0.5 N. At the end of 1'2 hours, sulfuric-acid of 25% strength is added until the mass is alkaline to brilliant yellow but neutral to cresol phthalein. Methanol is distilled off until the temperature of the liquid in the still is 105 C. Then 400 parts of hot 100 C.) water is added. The reaction mass is cooled under agitation to 30 C. The parachloro-o-nitro-anisole is separated by filtration, washed with water and dried. The product has a freezing point of about 96 C. and is obtained in a yield of about of the theoretical.

Example II 672 parts of 95% methanol, 2'7 parts of solid caustic soda of 95% strength and 192 parts of nitro-para-dichloro-benzene were added to a reaction vessel as described in Example I. The temperature was raised to 68 C. An aqueous solution of sodium hydroxide of 45% strength then was added as required to maintain the alkali concentration' at 0.8 N. The reaction was complete in three hours. The charge then was neutralized and the product isolated by the method described in Example I. The product had a freezing point of 92 C. and the yield was about 90% of the theoretical.

J. Many modifications may be made in the process without departing from the spirit of the invention: Any strong base, for instance potassium hydroxide, may replace wholly or in part the sodium hydroxide; the ratio of methanol to nitro-para-dichloro-benzene may be varied within wide limits, but it will be found that the higher this ratio the slower the rate of reaction under identical conditions of temperature and alkali concentrations; when the concentration of other reactants and the temperature are held constant, the higher the alkali concentration the more rapid is the condensation; the temperature at which the reaction is carried out may be varied, but the lower the temperaturethe slower condensation so temperatures near boiling are preferred. In our process it is possible to carry out the reaction at temperatures near boiling without the danger which accompanied attempts to carry out the older process because the close control which is kept over the addition of alkali .and Pabst the following advantages:

prevents the violent and dangerous reactions which made the older process unsatisfactory for plant use.

K. Our preferred conditions comprehend a ratio of about one part nitro-p-dichloro benzene to between three and four parts of methanol, temperatures between 68 and 71 C. and alkali concentrations of 0.25 to l N.

L. Any satisfactory method of isolating the product may be adopted. Among such methods are crystallization of the product by cooling the reaction mass, and fractional distillation of the neutralized reaction mass, and the one described in the examples.

M. The product of this reaction is used in the manufacture of dyes.

N. The process has over the method of Brand Sodium hydroxide is substituted for the more expensive potassium hydroxide used by those investigators, a substitution made possible by the close control which. we keep of the reaction; the addition of the alkali in the form of a strong aqueous solution instead of the more expensive and less convenient solution in methanol has both technical and financial advantage; a positive control of the rate of reaction is obtained by the use of specific alkali concentrations which are maintained throughout the process; and there is no hazard in manufacturing a large batch of material, despite the highly exothermic nature of the reaction.

0. As many apparently widely difierent embodiments of this invention may be made without departing from the spirit and scope thereof,

it is to be understood that We do not limit ourselves to the specific embodiments thereof except as defined by the appended claims.

We claim:

1. The process which comprises heating for about twelve hours at about 68 C. in a copper reaction vessel about 672 parts of 95% methyl alcohol, about 192 parts of nitro-para dichlorobenzene and about 17 parts of solid sodium hydroxide' 95% pure, adding a 45% sodium hydroxide solution as required to maintain the alkali concentration at .5 N, neutralizing the excess sodium hydroxide, and isolating the product.

'2. The process which comprises heating at about 68 C. in a siliceous reaction vessel a mixture of methyl alcohol, nitro-para-dichloro-ben- .zene and sodium hydroxide, the sodium hydroxide, being in an amount to constitute in the mixture a solution of about .5 N, and adding to the mixture the sodium hydroxide aqueous solution at substantially the rate at which the sodium hydroxide is used in reaction.

3. The method which comprises heating methyl alcohol, nitro-para-dichloro-benzene and sodium hydroxide, the concentration of alkali at the start of the reaction being beneath that at which undesirable side reactions and excessive temperatures are evolved, and in'which alkali is added during the course of the reaction at substantially the rate at which it is used.

MILES AUGUSTINUS DAHLEN. ELMER ELLSWORTH FLECK. 

